ALD processes are used to produce thin, conformal films having high thickness accuracy and step coverage. ALD utilizes a series of sequential, self-limiting surface reactions, each forming a monolayer of adsorbed precursor, to form the film. ALD provides atomic layer control and enables the films to be deposited on structures having high aspect ratios. ALD conventionally uses two or more gaseous precursors, each being sequentially introduced into a reaction chamber. A wide variety of materials may be deposited by ALD, many of which are used in the fabrication of semiconductor devices and integrated circuits (ICs).
In a conventional ALD process, at least one precursor is introduced to a substrate in a reaction chamber in alternate pulses separated by inert gas purging (in flow type reactors) or by evacuation of the reactor (in high-vacuum type reactors). The precursors react with surface groups on the substrate, or chemisorb on exposed surfaces of the substrate. The inert gas may then be flowed into the reaction chamber to substantially remove the precursor from the chamber before introducing another precursor.
The possibility of altering functional groups on surfaces of substrates, such as silicon substrates, enables selective deposition of materials on the substrate by ALD. For example, surface treatments may be used to increase reactivity of the surface of the substrate or to block deposition on regions of the surface of the substrate. Exposed regions of a patterned surface of the substrate may be selectively treated to yield reactive surface regions including reactive functional groups, such as, organic terminal groups, that improve nucleation of the precursors during the ALD process.
One example of selective deposition of materials using an ALD process is the patterning of hafnium dioxide (HfO2) on silicon using a blocking chemistry that involves siloxane attachment of compounds to surfaces of silicon dioxide (SiO2). For example, the silicon dioxide may be deposited on the silicon using conventional techniques and, thereafter, conventional lithographic techniques may be used to pattern the silicon dioxide so that areas of the silicon are exposed through the silicon dioxide. Surfaces of the silicon dioxide may be exposed to octadecyltrichlorosilane (ODTS) to form an octadecyltrichlorosilane monolayer on the surfaces of the silicon dioxide. An ALD process may then be performed to selectively form the hafnium oxide on the silicon, without the hafnium oxide forming on the octadecyltrichlorosilane monolayer overlying the silicon dioxide.
Selective deposition of materials using an ALD process has also been demonstrated using a patterned organic material. For example, platinum (Pt) may be selectively deposited on silicon by an ALD process using 1-octadecene as a blocking material. Silicon dioxide is deposited and patterned over the silicon using conventional techniques. The 1-octadecene may be adsorbed to the silicon exposed through the silicon dioxide to form a patterned surface including nonreactive organic regions (i.e., 1-octadecene regions) and reactive cleared regions (i.e., regions of exposed silicon). An ALD process may be performed to selectively deposit the platinum over the exposed silicon regions without the platinum depositing on the 1-octadecene regions.
However, the ability to pattern organic materials using conventional lithographic techniques is limited since it is only possible to alter functional groups or deposit materials on horizontal surfaces of the substrate, not on surfaces of recessed structures in the substrate. Furthermore, conventional blocking materials are often not compatible with conventional ALD processes. For example, platinum deposition using a conventional ALD process is performed at temperatures of greater than or equal to 300° C. and may use oxygen as a reactant. Under such conditions, conventional surface treatments may be damaged, degraded or removed from the surface of the substrate, especially during ALD processes having longer cycle times, which are used to deposit increased thicknesses of material. For instance, rapid degradation of self-assembled monolayers, such as octadecyltrichlorosilane and alkanethiol monolayers, during ALD processes has been observed. See Tatoulian et al., “Plasma Surface Modification of Organic Materials: Comparison between Polyethylene Films and Octadecyltrichlorosilane Self-Assembled Monolayers,” Langmuir, 20,10481 (2004); Xue and Yang, “Chemical Modifications of Inert Organic Monolayers with Oxygen Plasma for Biosensor Applications,” Langmuir, 23, 5831 (2007); Raiber et al., “Removal of Self-Assembled Monolayers of Alekanethiolates on Gold by Plasma Cleaning,” Surf. Sci., 595, 56 (2005); “Park et al., “Microcontact Patterning of Ruthenium Gate Electrodes by Selective Area Atomic Layer Deposition,” App. Phys. Lett., 86, 051903 (2005); and Lee et al., “Degradation of the Deposition Blocking Layer During Area-Selective Plasma-Enhanced Atomic Layer Deposition of Cobalt,” Journal of the Korean Physical Society, 56, 1 (2010).